RBMOnline - Vol 8. No 4. 2004 470-476 Reproductive BioMedicine Online; www.rbmonline.com/article/1232 on web 24 February 2004 Article Preimplantation genetic diagnosis in patients with male meiotic abnormalities Since 1986 Begoña Aran has been a senior embryologist in the IVF laboratory of the Medicine Reproduction Service of Institut Universitari Dexeus in Barcelona, Spain. She is Secretary of the Spanish Association of Biology of Reproduction (ASEBIR). Her particular research interest is in male infertility and IVF and she has published several articles in this field. Her thesis topic is Genetic risk in patients with oligoasthenozoospermia undergoing IVF-ICSI. Dr Begoña Aran B Aran 1,3, A Veiga 1, F Vidal 2, M Parriego 1,2, JM Vendrell 1, J Santaló 2, J Egozcue 2, PN Barri 1 1 Servei de Medicina de la Reproducció, Departament d Obstetricia i Ginecologia, Institut Universitari Dexeus, Passeig Bonanova 89 91, 08017 Barcelona, Spain 2 Unitat de Biologia Cellular, Facultat de Ciències, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain 3 Correspondence: Fax: +34 93 2057966; e-mail: begara@dexeus.com Abstract Indications and candidates for preimplantation genetic diagnosis (PGD) have increased in recent years. This study evaluates whether IVF intracytoplasmic sperm injection (ICSI) results could be improved by selecting embryos through PGD AS (aneuploidy screening) in couples in whom the male partner presents meiotic abnormalities. Two hundred and fifty-six embryos were biopsied and 183 were suitable for analysis (73.2%). Ninety-two embryos showed normal chromosomal analysis (50.3% of the analysed embryos and 57.5% of the diagnosed embryos). Pregnancy, abortion and implantation rates were compared with 66 IVF ICSI cycles performed in 44 patients with meiotic abnormalities without PGD (control group). No statistically significant differences in the pregnancy rate (52 versus 43.9%), implantation rate (32.1 versus 23.5%) and miscarriage rate (15.4 versus 10.3%) were observed between the groups. Although the embryos obtained from men with meiotic abnormalities showed a high frequency of chromosome abnormalities, no improvements in pregnancy and implantation rates were obtained after PGD AS in the series analysed. Keywords: ICSI, male meiotic abnormalities, PGD AS 470 Introduction Since 1990, when Handyside et al. reported the first pregnancy from biopsied preimplantation embryos, candidates and indications for preimplantation genetic diagnosis (PGD) have increased considerably (ESHRE PGD Consortium, 2002). Nowadays, PGD is not only used to avoid the transmission of genetic abnormalities, but also to improve IVF success rate in certain groups of patients (Gianaroli et al., 1999; Munné et al., 1999, 2003; Kuliev and Verlinsky, 2002; Munné, 2002). Some patients that could possibly benefit from PGD AS (aneuploidy screening) are couples in whom the male partner is affected by meiotic abnormalities (Aran et al., 2002). Meiotic studies have been incorporated as a cytogenetic diagnostic tool in the screening of male infertility since the early 1970s (Hultén et al., 1970; Pearson et al., 1970). Investigation of the meiotic division in spermatogenic cells from testicular biopsies resulted in the description of specific meiotic abnormalities limited to the germ cell line, affecting homologue chromosome pairing (synapsis) and recombination (revised by Egozcue et al., 2000) that have been related to mutations of one or more genes coding for specific meiotic products (for example, synaptonemal complex proteins, recombination enzymes, DNA repair enzymes; Edelmann et al., 1996; Hassold, 1996). Different groups have contributed to the characterization and classification of the different meiotic abnormalities described so far (revised by Templado et al., 1981). Taking into consideration that meiotic abnormalities are only detectable through cytogenetic studies in spermatocytes and that the information obtained can help to establish at a diagnosis, meiotic analysis has been included in some screening protocols of male infertility, especially since the reluctance of andrologists to obtain testicular material has clearly decreased. Meiotic disorders in spermatogenic cells have been found in 6% of infertile men in whom a meiotic analysis had been
indicated (Egozcue et al., 1983). This percentage rises to 17.5% in patients with oligoasthenoteratozoospermia (OAT) (Vendrell et al., 1999; Egozcue et al., 2000). Meiotic anomalies could lead to different degrees of meiotic arrest (partial or complete) clearly identified through the meiotic study, and usually reflected in an abnormal spermiogram, but also to non-disjunctionary events that could result in the production of unbalanced spermatozoa. In fact, this point is supported by data obtained from fluorescence in-situ hybridization (FISH) studies in decondensed sperm nuclei. Several groups have reported increases in sex chromosome disomies and diploid spermatozoa in patients with OA (oligoasthenozoospermia) and OAT undergoing IVF intracytoplasmic sperm injection (ICSI)cycles (Aran et al., 1999; Pang et al., 1999; Bernardini et al., 2000; Vegetti et al., 2000; Calogero et al., 2001; Rubio et al., 2001). Since the development of ICSI (Palermo et al., 1992), this micromanipulation technique has become the method of choice for the treatment of severe male factor infertility. ICSI solved the fertility problems of many of these patients, but opened a debate about the genetic risk for the offspring when patients affected by extremely severe and idiopathic male factors are treated (Meschede and Horst, 1997). Furthermore, in severely oligoasthenoteratozoospermic males with meiotic disorders, the theoretical risk could be increased by the possibility of generating chromosomally abnormal embryos due to the injection of abnormal spermatozoa. In a previous study (Aran et al., 2003), no statistical differences were found in the IVF ICSI pregnancy and implantation results in oligoasthenozoospermic patients with regard to the meiotic anomalies observed. Nevertheless, taking into account the risk of production of chromosomally abnormal spermatozoa (aneuploid, diploid), application of PGD could be useful in some patients showing meiotic abnormalities. In this context, cytogenetic analysis of embryos derived from these couples and further replacement of those evaluated as normal could result in an increase in the implantation and pregnancy rate, as well as in a decrease in the rate of chromosomal abnormalities in the offspring. Therefore, PGD was introduced for the reproductive treatment of couples with severe male factors associated with meiotic abnormalities, to evaluate if the use of PGD AS in these patients could result in an improvement of assisted reproductive success. This paper presents the results obtained in PGD AS cycles in couples in whom the males presented meiotic chromosomal anomalies. Pregnancy and implantation rates obtained in such couples are compared after PGD with a similar group in which PGD was not performed. Materials and methods The study group included 25 couples with severe male factor and meiotic abnormalities, undergoing 27 PGD AS. The control group comprised 44 couples with similar characteristics undergoing 66 ICSI cycles, but not referred for PGD. All patients enrolled in the study gave written consent to participate. Cytogenetic meiotic analysis Cytogenetic meiotic analysis is included in the protocol of study of infertile men at the Institut Universitari Dexeus and suggested to patients according to the andrologist's criteria (Vendrell et al., 1999). In all the patients included in this study, unilateral testicular biopsy for meiotic analysis was obtained under local anaesthesia. Testicular material was collected in isotonic solution (0.9% NaCl) and processed as previously described (Egozcue et al., 1983), based on the classical technique of Evans et al. (1964). Testicular tissue was chopped up with fine scissors in a Petri dish; material was transferred to a conical centrifuge tube containing hypotonic solution (0.075 mol/l KCl) and left to stand at room temperature to allow pieces of tubules to sediment. Supernatant was removed to a clean centrifuge tube, incubated at 37ºC for 20 min and centrifuged for 10 min at 800 rpm. The obtained pellet was resuspended in 5 8 ml of fixative (methanol acetic acid, 3:1) and kept at 4ºC for 30 min. The suspension was centrifuged as above, the supernatant discarded and the pellet resuspended in fixative. This procedure was repeated 2 or 4 times until clean. Finally, the pellet was resuspended in 1 2 ml of fixative and air-dried preparations were obtained by throwing 1 or 2 drops of the cell suspension onto clean degreased slides. Preparations were coded, stained by Leishman (1:4, in Leishman buffer) for 8 min, scored under a bright field microscope to locate meiotic figures at 10 and analysed at 100. Evaluation of the meiotic stages, chiasmata count and meiotic characterization was performed according to standard criteria (revised by Hultén et al., 2001), and meiotic abnormalities were classified according to Templado et al. (1981). Patients enrolled for PGD were selected from those presenting meiotic anomalies. ICSI cycles Follicular stimulation was carried out in all patients, using a combination of subcutaneous administrated gonadotrophinreleasing hormone agonist (GnRH) (Leuprolide, Procrin; Abbot, Madrid, Spain) with FSH (Neofertinorm; Serono, Madrid, Spain) and human chorionic gonadotrophin (HCG) (Profasi; Serono), as described previously (Barri et al., 1988). Oocytes were recovered by ultrasound-guided transvaginal follicle puncture 36 h after HCG injection (Carreras et al., 1994). All sperm samples were prepared with discontinuous gradients (Pure sperm; Nidacon, Göteborg, Sweden) (Ord et al., 1990). Oocyte preparation and ICSI procedure have been described previously (Calderón et al., 1995). Fertilization was assessed using a stereomicroscope (Olympus, SZH; Olympus España, Barcelona, Spain), 16 20 h after ICSI. 471
PGD protocol Embryo biopsies were performed at day 3. Each embryo was manipulated individually in EB medium (Vitrolife, Göteborg, Sweden) under oil (Ovoil; Vitrolife). The zona pellucida was drilled (diameter 25 30 µm) with the use of a laser (Fertilase) (Boada et al., 1998). A blastomere was gently aspirated with a glass needle (Humagen, Charlottesville, USA). The fixation method used was a slight modification of that described by Tarkowski (1966). Fixed blastomeres were processed for aneuploidy screening (Vidal et al. 1998). The PB multicolour probe panel (Vysis Inc., Downers Grove, IL, USA) plus a second round of FISH using satellite DNA probes for chromosomes X and Y (Vysis) were used for the evaluation of chromosomes (13, 16, 18, 21, 22, X, Y). Embryo transfer Normal diagnosed embryos were replaced on day 5. Surplus transferable embryos were cryopreserved. In the control group, embryos were replaced on day 2 according to the usual laboratory protocol. Luteal phase Luteal phase support was given by vaginal administration of natural micronized progesterone 600 mg/day (Utrogestan; Seid, Barcelona, Spain) for 10 days or HCG 2500 IU on days 2, 4 and 6 after oocyte retrieval. Pregnancy was evaluated by serum β-hcg concentration measured 12 and 21 days after replacement. An ultrasound scan was performed at 6 weeks of amenorrhoea for the detection of a gestational sac and fetal heart beat. Data set and statistics Results regarding pregnancy, implantation and miscarriage rates obtained in the PGD group for meiotic abnormalities were compared with the control group, using Fisher s exact test. In all cases 5% level of significance was chosen. Results All the males selected for the study displayed desynapsis of a variable number of chromosome bivalents (Templado et al., 1981) in the meiotic analysis performed. General characteristics of couples and cycles and a summary of the clinical outcome are described in Table 1. In the PGD cycles, women s ages ranged from 24 to 39 years, with a mean of 31.5. Men s mean age was 34.6 years, ranging from 28 to 51 years. A total of 519 oocytes were recovered (mean 19.2), 393 oocytes were microinjected (mean 14.6) and 293 (mean 10.9) showed 2PN between 16 and 20 h post-microinjection (74.5%). In the control group, women s mean age was 33.1 years (range 20 41) and men s mean age was 34.9 (range 21 59). Nine hundred and sixteen oocytes were recovered (mean 13.9), 735 oocytes were microinjected (mean 11.1) and 496 showed 2PN (mean 7.5; 67.5%). No statistically significant differences were found between the groups in any of the parameters studied. Results of PGD are shown in Table 2. Two hundred and fifty embryos were biopsied and 183 could be analysed (73.2%). Ninety-two embryos were normal for the chromosomes analysed (50.3% from the analysed embryos and 57.5% from the diagnosed embryos). Sixty-eight embryos were abnormal (37.2% from the analysed embryos and 42.5% from the diagnosed embryos). Twenty-three embryos (12.7%) had an inconclusive diagnosis, usually due to non-informative results Table 1. General characteristics and clinical outcome of couples with meiotic abnormalities after ICSI cycles with and without PGD. There were no significant differences between groups. Meiotic abnormalities with PGD Meiotic abnormalities without PGD No. couples 25 44 No. cycles 27 66 Mean age male (years)34.6 (28 51)34.9 (21 59) Mean age female (years)31.5 (24 39)33.1 (20 41) Mean oocytes recovered (no. oocytes)19.2 (519) 13.9 (916) Mean oocytes microinjected (no. oocytes)14.6 (393) 11.1 (735) Mean 2PN oocytes (no. oocytes 2PN; %)10.9 (293; 74.5) 7.5 (496; 67.5) No. replacements 25 66 Mean no. embryos/transfer 2.1 2.8 No. pregnancies 13 29 Pregnancy rate/cycle (%)48.1 43.9 Pregnancy rate/transfer (%)52.0 43.9 Implantation rate (%)32.1 23.5 Miscarriage rate (%)15.4 10.3 472
Table 2. Embryo analysis results. No. cycles 27 No. biopsied embryos 250 No. analysed embryos (%)183 (73.2) No. diagnosed embryos (%)160 (87.4) No. normal embryos (%)92 (57.5) No. abnormal embryos (%)68 (42.5) No. undiagnosed embryos (%)23 (12.6) Table 3. Abnormalities found in the abnormal embryos after PGD for meiotic abnormalities. Abnormalities Haploid embryos 5 Polyploid embryos 4 Chromosome 13 Monosomies 1 Trisomies 4 Chromosome 16 Nullisomies 1 Monosomies 2 Chromosome 18 Nullisomies 1 Monosomies 4 Trisomies 10 Tetrasomies 1 Chromosome 21 Monosomies 3 Trisomies 3 Chromosome 22 Trisomies 2 Chromosome X Monosomies 3 Trisomies 2 Tetrasomies 1 Chromosome Y Disomies 3 Mosaic embryos a 6 Complex aneuploidies b 12 No. embryos a Discordant results obtained after the analysis of two blastomeres. b Affecting several of the chromosomes analysed. for one of the chromosome pairs analysed (Table 2). Sixtyseven embryos (26.8%) could not be analysed due to the characteristics of the nuclei obtained after fixation. Details of embryo chromosome abnormalities are shown in Table 3 and Figure 1. Five embryos analysed were haploid and four embryos were polyploid. Nine embryos showed abnormalities of the sex chromosomes. Five embryos had abnormalities affecting chromosome 13, three embryos affecting chromosome 16, 16 embryos chromosome 18, six embryos showed anomalies affecting chromosome 21 and two embryos chromosome 22. Twelve embryos presented abnormalities affecting several of the chromosomes analysed (complex aneuploidies). Discordant results were obtained after the analysis of two blastomeres in six embryos (considered as mosaic). Figure 2 shows frequencies of total anomalies found. Ninety-three embryos were replaced in 25 transfers in the PGD group for meiotic abnormalities (2.1 embryos/transfer), resulting in 13 pregnancies. This represents 48.1% pregnancy rate per cycle and 52% pregnancy rate per transfer. The implantation rate was 32.1%. Two pregnancies ended in miscarriages (15.4%) (Table 1) In the control group, 29 pregnancies were achieved from 66 IVF ICSI cycles: 43.9% of pregnancy rate per cycle and per transfer. Implantation rate was 23.5%. Miscarriage rate was 10.3% (Table 1). There were no significant differences in the pregnancy rate, implantation rate and miscarriage rate between the two groups. Discussion The data obtained in this series indicate that embryos from patients with meiotic abnormalities subject to ICSI have a high number of chromosome anomalies (42.5%). Gianaroli et al. (1997) did not find differences in the percentage of abnormal embryos after PGD in ICSI patients versus conventional IVF patients, or when the same authors (Gianaroli et al., 2000) compared PGD results between normozoospermic patients versus oligoasthenozoospermic patients. They found differences in patients with abnormal karyotype, but they did not study patients with meiotic abnormalities. Kahraman et al. (2002), observed a percentage of abnormal embryos (41.3%) very similar to that observed in the present study (42.5%) in severe male infertility. The authors analysed the relationship between chromosome abnormalities and pronuclear morphology in severe male infertility. However, this group of patients is quite different from the present group. The present study analyses only patients with meiotic anomalies, whereas Kahraman studied patients with different categories of male infertility and used ejaculated spermatozoa, testicular spermatozoa or even round spermatids for fertilization. Silber et al. (2003) reported a high incidence of mosaicism in embryos derived from testicular sperm extraction (TESE) in men with a severe deficit in spermatogenesis (53% in TESE cycles versus 26.5% in ICSI cycles with ejaculated spermatozoa). The aneuploidy rates were not statistically different between the groups (17 versus 26.2% respectively) and were rather lower than in the present study (42.5%), but the studies cannot be compared, because Silber et al. analysed patients with non-obstructive azoospermia and the present study involves patients with meiotic abnormalities. Gianaroli et al. (2001) found lower frequencies of normal embryos (57.5%) after PGD for several indications, 30% in PGD for maternal age and in micro-epididymal sperm aspiration (MESA)/TESE patients and 28% of normal embryos in PGD for recurrent abortions. Munné et al. (2002) found similar percentages (39.7%) of normal embryos after PGD for maternal age. Rubio et al. (2003) found statistical differences comparing percentages of normal embryos after 473
Figure 1. Chromosome abnormalities in the 68 abnormal embryos. Figure 2. Percentage of abnormalities in abnormal embryos (some abnormalities were found in the same embryo). 474 PGD for recurrent miscarriage (29.3%) and for sex-linked diseases (45.1%). Regarding aneuploidy frequencies, aneuploidy of chromosome 18 was the most frequently observed (13.1%) in the present study, while the aneuploidy rate of sex chromosomes was not especially high (13.2%). These results are lower than those reported by Gianaroli et al. (2001), which rise to 32% in PGD for maternal age. Rubio et al. (2003) found similar percentages of chromosome 18 aneuploidy (10.1%) in recurrent miscarriage patients and in their control group (sex-linked disease) (9.5%). However, these authors reported a higher frequency of sex chromosome aneuploidy (10.9% in both groups) and found higher incidences of aneuploidies for other chromosomes such as 16, 21, 13 and 22 (25.1, 24.1, 20.1 and 19.7% respectively) in the recurrent miscarriage group. In the control group, frequencies of aneuploidy of these chromosomes were also higher than in the present series; 13.8 versus 6.9% for chromosome 13, 10.6 versus 4.8% for chromosome 16, 19.8 versus 13.1% for chromosome 21 and 8.6 versus 6.25% for chromosome 22. Although all authors used the same probes as used in the present study, all of them found lower percentages of normal embryos and higher frequencies of aneuploidies for the chromosomes analysed. These authors studied groups of patients with other indications for PGD, such as high maternal age or recurrent abortions. Perhaps the group of patients studied here present aneuploidies for other chromosomes, and other probes should be considered, to try to characterize abnormalities that may be characteristic of these patients. In addition, it may be necessary to adjust the probes used for each PGD indication. Regarding the results for haploid (3.1%) and polyploid (2.5%) embryos, the data are similar to those reported by Rubio et al. (2003) (4.7 and 1.6% respectively). Gianaroli et al. (2001) reported a significantly higher frequency of polyploidy (11%) in PGD for repeated IVF failures. Pregnancy rates as well as implantation rates were higher when embryos normal for the chromosomes studied were replaced in patients with meiotic abnormalities subject to PGD than in those who were not (52 versus 43.9% and 32.1 versus 23.5% respectively), even though the differences observed were not statistically significant. If normal embryos could be selected using adequate probes, pregnancy and implantation rate could be increased with statistically significant differences. Screening of patients before ICSI is important to assess their genetic risk. Meiotic studies incorporating multiplex FISH analysis (Sarrate et al., 2004) and FISH in ejaculated spermatozoa or the combination of both techniques (Vidal et al., 2003) are highly recommended, and should be considered as part of the genetic study in these patients. Correlations between these studies and the results of larger series will help to determine the real utility of PGD in severe male factor with meiotic impairment. Reproductive counselling and further strategies should consider the results obtained in the genetic study. In this sense, PGD should be advised in cases with a high genetic risk, in order to increase the chance of replacement of chromosomally normal embryos and to achieve adequate pregnancy rates.
Acknowledgements This study was supported by the Cátedra de Investigación en Obstetrícia y Ginecología of the Institut Universitari Dexeus, Barcelona, Spain and project SAF 2003-04312 (Dirección General de Investigación, Ministerio de Ciencia y Tecnología, Spain). References Aran B, Blanco J, Vidal F et al. 1999 Screening for abnormalities of chromosomes X,Y and 18 and for diploidy in spermatozoa from infertile men participating in an in vitro fertilization intracytoplasmic sperm injection program. Fertility and Sterility 72, 696 701. Aran B, Vidal F, Vendrell JM et al. 2002 Preimplantation genetic diagnosis in patients with meiotic abnormalities. 18th Annual Meeting of the European Society of Human Reproduction and Embryology, Vienna, Austria, 1 3 July, abstract P-156. Aran B, Vidal F, Vendrell JM et al. 2003 Outcome of intracytoplasmic sperm injection in relation to the meiotic pattern in patients with severe oligoasthenozoospermia. Fertility and Sterility 80, 91 95. Barri PN, Martinez F, Coroleu B et al. 1988 Experiencia clínica de la utilización de agonistas de la GnRh en un programa de FIV. Drugs Today 24 (suppl. 2), 51 60. Bernardini L, Gianaroli L, Fortini D et al. 2000 Frequency of hyper-, hypohaploidy and diploidy in ejaculate, epididymal and testicular germ cells of infertile patients. Human Reproduction 10, 2165 2172. Boada M, Carrera M, De La Iglesia C et al. 1998 Successful use of laser for human embryo biopsy in preimplantation genetic diagnosis: report of two cases. Journal of Assisted Reproduction and Genetics 15, 302 307. Calderón G, Belil I, Arán B et al. 1995 Intracytoplasmic sperm injection versus conventional in vitro fertilization: first results. Human Reproduction 10, 2835 2839. Calogero AE, De Palma A, Grazioso C et al. 2001 High sperm aneuploidy rate in unselected infertile patients and its relationship with intracytoplasmic sperm injection outcome. Human Reproduction 16, 1433 1439. Carreras O, Pascual MA, Hereter L, Barri PN 1994 4000 Punciones Ecográficas para el Programa de Fiv del Institut Universitari Dexeus. Libro XVII Reunión Nacionale de la Sección de Ecografía de la Sego 65. Edelmann W, Cohen PE, Kane M et al. 1996 Meiotic pachytene arrest in MLH-deficient mice. Cell 85, 1125 1134. Egozcue J, Templado C, Vidal F et al. 1983 Meiotic studies in a series of 1100 infertile and sterile males. Human Genetics 65, 185 188. Egozcue S, Vendrell JM, Garcia F et al. 2000 Increased incidence of meiotic anomalies in oligoasthenozoospermic males preselected for intracytoplasmic sperm injection. Journal of Assisted Reproduction and Genetics 17, 307 309. ESHRE PGD Consortium Steering Committee 2002 ESHRE Preimplantation Genetic Diagnosis Consortium: data collection III (May 2001). Human Reproduction 17, 233 246. Evans EP, Breckon G, Ford CE 1964 An air-drying method of meiotic preparations from mammalians testes. Cytogenetics 3, 289 294. Gianaroli L, Munné S, Magli MC, Ferraretti AP 1997 Preimplantation genetic diagnosis of aneuplody and male infertility. International Journal of Andrology 20, 31 34. Gianaroli L, Magli MC, Ferrareti AP, Munné S 1999 Preimplantation diagnosis for aneuploidies in patients undergoing in vitro fertilization with a poor prognosis: identification of the categories for which it should be propose. Fertility and Sterility 72, 837 844. Gianaroli L, Magli MC, Ferraretti AP, Iammarrone E 2000 Preimplantation diagnosis after assisted reproduction techniques for genetically-determined male infertility. Journal of Endocrinological Investigation 23, 711 716. Gianaroli L, Magli MC, Ferraretti AP et al. 2001 The role of preimplantation diagnosis for aneuploidies. Reproductive BioMedicine Online 4, 31 36. Handyside AH, Kontogianni EH, Hardy K, Winston RML 1990 Pregnancies from biopsied human preimplantation embryos sexed by Y-specific DNA amplification. Nature 244, 768 770. Hassold TJ 1996 Mismatch repair goes meiotic. Nature Genetics 13, 261 262. Hultén M, Eliasson R, Tillinger KG 1970 Low chiasma count and other meiotic irregularities in two infertile 46,XY men with spermatogenic arrest. Hereditas 65, 285 290. Hultén M, Barlow A, Tease C 2001 Meotic studies in human. In: Rosney DE (ed.) Human Cytogenetics: Constitutional Analysis. A Partial Approach. Oxford University Press, Oxford, pp. 211 236. Kahraman S, Kumtepe Y, Sertyel S et al. 2002 Pronuclear morphology scoring and chromosomal status of embryos in severe male infertility. Human Reproduction 17, 3193 3200. Kuliev A, Verlinsky Y 2002 Current features of preimplantation genetic diagnosis. Reproductive BioMedicine Online 5, 294 299. Meschede D, Horst J 1997 Genetic counselling for infertile male patients. International Journal of Andrology 20, 20 30. Munné S 2002 Preimplantation genetic diagnosis of numerical and structural chromosome abnormalities. Reproductive BioMedicine Online 4, 183 196. Munné S, Magli C, Cohen J et al. 1999 Positive outcome after preimplantation diagnosis of aneuploidies in human embryos. Human Reproduction 14, 2191 2199. Munné S, Sandalinas M, Escudero T et al. 2002 Chromosome mosaicism in cleavage-stage human embryos: evidence of a maternal age effect. Reproductive BioMedicine Online 4, 223 232. Munné S, Sandalinas M, Escudero T et al. 2003 Improved implantation after preimplantation genetic diagnosis of aneuploidy. Reproductive BioMedicine Online 7, 91 97. Ord T, Patrizio P, Morello E et al. 1990 Mini-Percoll: a new method for semen preparation IVF in severe male factor infertility. Human Reproduction 5, 987 989. Palermo G, Joris H, Devroey P, Van Steirteghem AC 1992 Pregnancies after intracytoplasmic injection of single spermatozoa into an oocyte. Lancet 340, 17 18. Pang MG, Hoegerman SF, Cuticchia AJ et al. 1999 Detection of aneuploidy for chromosomes 4, 6, 7, 8, 9, 10, 11, 12, 13, 17, 18, 21, X and Y by fluorescence in-situ hybridisation in spermatozoa from nine patients with oligoasthenoteratozoospermia undergoing intracytoplasmic sperm injection. Human Reproduction 14, 1266 1273. Pearson PL, Ellis JD, Evans HJ 1970 A gross reduction in chiasma formation during meiotic prophase and a defective DNA repair mechanism associated with a case of human male infertility. Cytogenetics 9, 460 467. Rubio C, Gil-Salom M, Simón C et al. 2001 Incidence of sperm chromosomal abnormalities in a risk population: relationship with sperm quality and ICSI outcome. Human Reproduction 6, 2084 2092. Rubio C, Simón C, Vidal F et al. 2003 Chromosomal abnormalities and embryo development in recurrent miscarriage couples. Human Reproduction 18, 182 188. Sarrate Z, Blanco J, Egozcue S et al. 2004 Identification of meiotic anomalies using multiplex FISH: preliminary results. Fertility and Sterility, in press. Silber S, Escudero T, Lenahan K et al. 2003 Chromosomal abnormalities in embryos derived from testicular sperm extraction. Fertility and Sterility 79, 30 38. Tarkowski AK 1966 An air-drying method for chromosome preparations from mouse eggs. Cytogenetics 5, 394 400. Templado C, Vidal F, Marina S et al. 1981 A new meiotic mutation: desynapsis of individual bivalents. Human Genetics 59, 345 348. Vegetti W, Van Assche E, Frias A et al. 2000 Correlation between semen parameters and sperm aneuploidy rates investigated by 475
fluorescence in-situ hybridisation in infertile men. Human Reproduction 15, 351 365. Vendrell JM, García F, Veiga A et al. 1999 Meiotic abnormalities and spermatogenic parameters in severe oligoasthenozoospermia. Human Reproduction 14, 375 378. Vidal F, Gimenez C, Rubio C et al. 1998 FISH preimplantation diagnosis of chromosome aneuploidy in recurrent pregnancy wastage. Journal of Assisted Reproduction and Genetics 15, 310 313. Vidal F, Sarrate Z, Blanco J et al. 2003 Multi-FISH analysis of meiotic anomalies. Human Reproduction 18, O-202. Received 16 December 2003; refereed 7 January 2004; accepted 10 February 2004. 476